arch/arm64/kvm/fpsimd.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers
  *
  * Copyright 2018 Arm Limited
  * Author: Dave Martin <Dave.Martin@arm.com>
  */
 #include <linux/irqflags.h>
 #include <linux/sched.h>
 #include <linux/kvm_host.h>
 #include <asm/fpsimd.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 #include <asm/sysreg.h>

 /*
  * Called on entry to KVM_RUN unless this vcpu previously ran at least
  * once and the most recent prior KVM_RUN for this vcpu was called from
  * the same task as current (highly likely).
  *
  * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
  * such that on entering hyp the relevant parts of current are already
  * mapped.
  */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 {
 	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
 	int ret;

 	/* pKVM has its own tracking of the host fpsimd state. */
 	if (is_protected_kvm_enabled())
 		return 0;

 	/* Make sure the host task fpsimd state is visible to hyp: */
 	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
 	if (ret)
 		return ret;

 	return 0;
 }

 /*
  * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
  * The actual loading is done by the FPSIMD access trap taken to hyp.
  *
  * Here, we just set the correct metadata to indicate that the FPSIMD
  * state in the cpu regs (if any) belongs to current on the host.
  */
 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 {
 	BUG_ON(!current->mm);

 	if (!system_supports_fpsimd())
 		return;

 	fpsimd_kvm_prepare();

 	/*
 	 * We will check TIF_FOREIGN_FPSTATE just before entering the
 	 * guest in kvm_arch_vcpu_ctxflush_fp() and override this to
 	 * FP_STATE_FREE if the flag set.
 	 */
 	*host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED;
 	*host_data_ptr(fpsimd_state) = kern_hyp_va(&current->thread.uw.fpsimd_state);

 	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
 	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
 		vcpu_set_flag(vcpu, HOST_SVE_ENABLED);

 	if (system_supports_sme()) {
 		vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
 		if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
 			vcpu_set_flag(vcpu, HOST_SME_ENABLED);

 		/*
 		 * If PSTATE.SM is enabled then save any pending FP
 		 * state and disable PSTATE.SM. If we leave PSTATE.SM
 		 * enabled and the guest does not enable SME via
 		 * CPACR_EL1.SMEN then operations that should be valid
 		 * may generate SME traps from EL1 to EL1 which we
 		 * can't intercept and which would confuse the guest.
 		 *
 		 * Do the same for PSTATE.ZA in the case where there
 		 * is state in the registers which has not already
 		 * been saved, this is very unlikely to happen.
 		 */
 		if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
 			*host_data_ptr(fp_owner) = FP_STATE_FREE;
 			fpsimd_save_and_flush_cpu_state();
 		}
 	}

 	/*
 	 * If normal guests gain SME support, maintain this behavior for pKVM
 	 * guests, which don't support SME.
 	 */
 	WARN_ON(is_protected_kvm_enabled() && system_supports_sme() &&
 		read_sysreg_s(SYS_SVCR));
 }

 /*
  * Called just before entering the guest once we are no longer preemptible
  * and interrupts are disabled. If we have managed to run anything using
  * FP while we were preemptible (such as off the back of an interrupt),
  * then neither the host nor the guest own the FP hardware (and it was the
  * responsibility of the code that used FP to save the existing state).
  */
 void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
 {
 	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
 		*host_data_ptr(fp_owner) = FP_STATE_FREE;
 }

 /*
  * Called just after exiting the guest. If the guest FPSIMD state
  * was loaded, update the host's context tracking data mark the CPU
  * FPSIMD regs as dirty and belonging to vcpu so that they will be
  * written back if the kernel clobbers them due to kernel-mode NEON
  * before re-entry into the guest.
  */
 void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
 {
 	struct cpu_fp_state fp_state;

 	WARN_ON_ONCE(!irqs_disabled());

 	if (guest_owns_fp_regs()) {
 		/*
 		 * Currently we do not support SME guests so SVCR is
 		 * always 0 and we just need a variable to point to.
 		 */
 		fp_state.st = &vcpu->arch.ctxt.fp_regs;
 		fp_state.sve_state = vcpu->arch.sve_state;
 		fp_state.sve_vl = vcpu->arch.sve_max_vl;
 		fp_state.sme_state = NULL;
 		fp_state.svcr = &vcpu->arch.svcr;
 		fp_state.fpmr = &vcpu->arch.fpmr;
 		fp_state.fp_type = &vcpu->arch.fp_type;

 		if (vcpu_has_sve(vcpu))
 			fp_state.to_save = FP_STATE_SVE;
 		else
 			fp_state.to_save = FP_STATE_FPSIMD;

 		fpsimd_bind_state_to_cpu(&fp_state);

 		clear_thread_flag(TIF_FOREIGN_FPSTATE);
 	}
 }

 /*
  * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
  * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
  * disappears and another task or vcpu appears that recycles the same
  * struct fpsimd_state.
  */
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 {
 	unsigned long flags;

 	local_irq_save(flags);

 	/*
 	 * If we have VHE then the Hyp code will reset CPACR_EL1 to
 	 * the default value and we need to reenable SME.
 	 */
 	if (has_vhe() && system_supports_sme()) {
 		/* Also restore EL0 state seen on entry */
 		if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
 			sysreg_clear_set(CPACR_EL1, 0, CPACR_ELx_SMEN);
 		else
 			sysreg_clear_set(CPACR_EL1,
 					 CPACR_EL1_SMEN_EL0EN,
 					 CPACR_EL1_SMEN_EL1EN);
 		isb();
 	}

 	if (guest_owns_fp_regs()) {
 		if (vcpu_has_sve(vcpu)) {
 			__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);

 			/*
 			 * Restore the VL that was saved when bound to the CPU,
 			 * which is the maximum VL for the guest. Because the
 			 * layout of the data when saving the sve state depends
 			 * on the VL, we need to use a consistent (i.e., the
 			 * maximum) VL.
 			 * Note that this means that at guest exit ZCR_EL1 is
 			 * not necessarily the same as on guest entry.
 			 *
 			 * Restoring the VL isn't needed in VHE mode since
 			 * ZCR_EL2 (accessed via ZCR_EL1) would fulfill the same
 			 * role when doing the save from EL2.
 			 */
 			if (!has_vhe())
 				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
 						       SYS_ZCR_EL1);
 		}

 		/*
 		 * Flush (save and invalidate) the fpsimd/sve state so that if
 		 * the host tries to use fpsimd/sve, it's not using stale data
 		 * from the guest.
 		 *
 		 * Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the
 		 * context unconditionally, in both nVHE and VHE. This allows
 		 * the kernel to restore the fpsimd/sve state, including ZCR_EL1
 		 * when needed.
 		 */
 		fpsimd_save_and_flush_cpu_state();
 	} else if (has_vhe() && system_supports_sve()) {
 		/*
 		 * The FPSIMD/SVE state in the CPU has not been touched, and we
 		 * have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
 		 * reset by kvm_reset_cptr_el2() in the Hyp code, disabling SVE
 		 * for EL0.  To avoid spurious traps, restore the trap state
 		 * seen by kvm_arch_vcpu_load_fp():
 		 */
 		if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
 			sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
 		else
 			sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
 	}

 	local_irq_restore(flags);
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers
	*
	* Copyright 2018 Arm Limited
	* Author: Dave Martin <Dave.Martin@arm.com>
	*/
	#include <linux/irqflags.h>
	#include <linux/sched.h>
	#include <linux/kvm_host.h>
	#include <asm/fpsimd.h>
	#include <asm/kvm_asm.h>
	#include <asm/kvm_hyp.h>
	#include <asm/kvm_mmu.h>
	#include <asm/sysreg.h>

	/*
	* Called on entry to KVM_RUN unless this vcpu previously ran at least
	* once and the most recent prior KVM_RUN for this vcpu was called from
	* the same task as current (highly likely).
	*
	* This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
	* such that on entering hyp the relevant parts of current are already
	* mapped.
	*/
	int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
	{
	struct user_fpsimd_state *fpsimd = &current->thread.uw.fpsimd_state;
	int ret;

	/* pKVM has its own tracking of the host fpsimd state. */
	if (is_protected_kvm_enabled())
	return 0;

	/* Make sure the host task fpsimd state is visible to hyp: */
	ret = kvm_share_hyp(fpsimd, fpsimd + 1);
	if (ret)
	return ret;

	return 0;
	}

	/*
	* Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
	* The actual loading is done by the FPSIMD access trap taken to hyp.
	*
	* Here, we just set the correct metadata to indicate that the FPSIMD
	* state in the cpu regs (if any) belongs to current on the host.
	*/
	void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
	{
	BUG_ON(!current->mm);

	if (!system_supports_fpsimd())
	return;

	fpsimd_kvm_prepare();

	/*
	* We will check TIF_FOREIGN_FPSTATE just before entering the
	* guest in kvm_arch_vcpu_ctxflush_fp() and override this to
	* FP_STATE_FREE if the flag set.
	*/
	*host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED;
	*host_data_ptr(fpsimd_state) = kern_hyp_va(&current->thread.uw.fpsimd_state);

	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
	vcpu_set_flag(vcpu, HOST_SVE_ENABLED);

	if (system_supports_sme()) {
	vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
	if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
	vcpu_set_flag(vcpu, HOST_SME_ENABLED);

	/*
	* If PSTATE.SM is enabled then save any pending FP
	* state and disable PSTATE.SM. If we leave PSTATE.SM
	* enabled and the guest does not enable SME via
	* CPACR_EL1.SMEN then operations that should be valid
	* may generate SME traps from EL1 to EL1 which we
	* can't intercept and which would confuse the guest.
	*
	* Do the same for PSTATE.ZA in the case where there
	* is state in the registers which has not already
	* been saved, this is very unlikely to happen.
	*/
	if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK \| SVCR_ZA_MASK)) {
	*host_data_ptr(fp_owner) = FP_STATE_FREE;
	fpsimd_save_and_flush_cpu_state();
	}
	}

	/*
	* If normal guests gain SME support, maintain this behavior for pKVM
	* guests, which don't support SME.
	*/
	WARN_ON(is_protected_kvm_enabled() && system_supports_sme() &&
	read_sysreg_s(SYS_SVCR));
	}

	/*
	* Called just before entering the guest once we are no longer preemptible
	* and interrupts are disabled. If we have managed to run anything using
	* FP while we were preemptible (such as off the back of an interrupt),
	* then neither the host nor the guest own the FP hardware (and it was the
	* responsibility of the code that used FP to save the existing state).
	*/
	void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
	{
	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
	*host_data_ptr(fp_owner) = FP_STATE_FREE;
	}

	/*
	* Called just after exiting the guest. If the guest FPSIMD state
	* was loaded, update the host's context tracking data mark the CPU
	* FPSIMD regs as dirty and belonging to vcpu so that they will be
	* written back if the kernel clobbers them due to kernel-mode NEON
	* before re-entry into the guest.
	*/
	void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
	{
	struct cpu_fp_state fp_state;

	WARN_ON_ONCE(!irqs_disabled());

	if (guest_owns_fp_regs()) {
	/*
	* Currently we do not support SME guests so SVCR is
	* always 0 and we just need a variable to point to.
	*/
	fp_state.st = &vcpu->arch.ctxt.fp_regs;
	fp_state.sve_state = vcpu->arch.sve_state;
	fp_state.sve_vl = vcpu->arch.sve_max_vl;
	fp_state.sme_state = NULL;
	fp_state.svcr = &vcpu->arch.svcr;
	fp_state.fpmr = &vcpu->arch.fpmr;
	fp_state.fp_type = &vcpu->arch.fp_type;

	if (vcpu_has_sve(vcpu))
	fp_state.to_save = FP_STATE_SVE;
	else
	fp_state.to_save = FP_STATE_FPSIMD;

	fpsimd_bind_state_to_cpu(&fp_state);

	clear_thread_flag(TIF_FOREIGN_FPSTATE);
	}
	}

	/*
	* Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
	* cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
	* disappears and another task or vcpu appears that recycles the same
	* struct fpsimd_state.
	*/
	void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
	{
	unsigned long flags;

	local_irq_save(flags);

	/*
	* If we have VHE then the Hyp code will reset CPACR_EL1 to
	* the default value and we need to reenable SME.
	*/
	if (has_vhe() && system_supports_sme()) {
	/* Also restore EL0 state seen on entry */
	if (vcpu_get_flag(vcpu, HOST_SME_ENABLED))
	sysreg_clear_set(CPACR_EL1, 0, CPACR_ELx_SMEN);
	else
	sysreg_clear_set(CPACR_EL1,
	CPACR_EL1_SMEN_EL0EN,
	CPACR_EL1_SMEN_EL1EN);
	isb();
	}

	if (guest_owns_fp_regs()) {
	if (vcpu_has_sve(vcpu)) {
	__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);

	/*
	* Restore the VL that was saved when bound to the CPU,
	* which is the maximum VL for the guest. Because the
	* layout of the data when saving the sve state depends
	* on the VL, we need to use a consistent (i.e., the
	* maximum) VL.
	* Note that this means that at guest exit ZCR_EL1 is
	* not necessarily the same as on guest entry.
	*
	* Restoring the VL isn't needed in VHE mode since
	* ZCR_EL2 (accessed via ZCR_EL1) would fulfill the same
	* role when doing the save from EL2.
	*/
	if (!has_vhe())
	sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
	SYS_ZCR_EL1);
	}

	/*
	* Flush (save and invalidate) the fpsimd/sve state so that if
	* the host tries to use fpsimd/sve, it's not using stale data
	* from the guest.
	*
	* Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the
	* context unconditionally, in both nVHE and VHE. This allows
	* the kernel to restore the fpsimd/sve state, including ZCR_EL1
	* when needed.
	*/
	fpsimd_save_and_flush_cpu_state();
	} else if (has_vhe() && system_supports_sve()) {
	/*
	* The FPSIMD/SVE state in the CPU has not been touched, and we
	* have SVE (and VHE): CPACR_EL1 (alias CPTR_EL2) has been
	* reset by kvm_reset_cptr_el2() in the Hyp code, disabling SVE
	* for EL0. To avoid spurious traps, restore the trap state
	* seen by kvm_arch_vcpu_load_fp():
	*/
	if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
	sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
	else
	sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
	}

	local_irq_restore(flags);
	}